1. Field of the Invention
The present invention pertains to apparatus for operating on wells, such as in workover operations. More particularly, the present invention relates to coiled tubing systems for injecting and extracting continuous tubing into and out of wells in various well servicing operations.
2. Description of Prior Art
Coiled tubing systems for working on wells are generally known. In such systems, a continuous metal tubing is driven down the well by way of an injector head. A pair of continuous-chain tube gripping dog assemblies are motor driven in the injector head to grip the tubing and move it down the well. Reverse operation of the chain dog assemblies is used to withdraw the tubing from the well. On the surface, the tubing is stored on a large drum or reel from which the tubing is withdrawn by the pull of the injector head. The reel is motor driven to rewind the tubing as it is withdrawn from the well.
The injector head is usually positioned on a mast over the Christmas tree of the well. A pair of hydraulic cylinder assemblies is used to vary the elevation of the injector head along the mast to accomodate the height of the Christmas tree as well as a blowout preventer added to the well for the coiled tubing workover operation.
While the entire coiled tubing system may be assembled in place at the well, mobile systems are available. In the latter case, the mast is mounted, for example, at the back of a truck bed with the reel positioned toward the opposite end of the bed. For transportation purposes the mast is folded or pivoted toward a generally horizontal position. When this is done, the injector head is also titlted with the mast. Since the injector head is not rigidly mounted on the mast, thereby allowing some lateral movement of the head relative to the mast, such a tilting operation involving the injector head is inherently dangerous. Furthermore, prior art systems with foldable masts are so designed that the injector head may not be lowered to the level of the truck bed.
A level wind tubing guide mechanism provided for guiding the tubing onto and off of the reel generally extends, in its operating position, to a height in excess of any desired road clearance value. Consequently, the level wind guide assembly must be tilted backwardly against the reel, for example, to permit highway transportation of the system.
The tilting of the injector head as well as the level wind guide mechanism in a transportation configuration necessitates the disengagement of the tubing from the injector head and its complete winding on the reel. Consequently, in such prior art mobile coiled tubing systems, the tubing must be connected through the injector head each time the system is to be used on a different well, and must be removed from the injector head and the level wind guide assembly each time the system is to be moved. Also, since the injector head is pivoted with the mast, the head is generally not available for servicing at a low elevation yet in an upright configuration. Furthermore current versions of coiled tubing assemblies generally provide only elevational as well as forward and backward adjustments for positioning the injector head; the truck must be generally maneuvered to effect any substantial sideways position adjustment for the injector head.
Even in the case of mobile coiled tubing systems known in the art, the blowout preventer used in such well working operations must be moved into position separately from the coiled tubing system. This often requires manhandling the blowout preventer.